This invention relates to air cleaning means for use with an internal combustion engine which adsorbs fuel vapors produced in the carburetor and intake manifold to avoid the release of hydrocarbons to atmosphere.
Heretofore, in order to avoid the release of hydrocarbons to atmosphere from internal combustion engines by adsorbing on an air cleaner element fuel vapors produced in the carburetor and intake manifold, proposals have been made to use various air cleaner element structures. The air cleaner element structures known in the art include: (1) an air cleaner filter element mounted in an air cleaner case and divided into two or more constituent parts, one part containing active carbon in particulate form, (2) a filter element including a folded filter material layer packed with active carbon in particulate form between the folds, and (3) an arrangement in which active carbon in particulate form is mounted in the interior of an inlet pipe of the air cleaner case or in the vicinity of the carburetor mounting portion of the air cleaner case so as to adsorb fuel vapors produced in the carburetor and intake manifold and flowing to the air cleaner element.
Some disadvantages are associated with these air cleaner element structures of the prior art. If active carbon in particulate form is arranged in the air cleaner case as proposed in the structures of (1) and (3), the vibration of the engine would be directly transmitted to the particulate active carbon in a construction in which the air cleaner case is directly mounted on the carburetor, with the result that wear would be caused on the particulate active carbon by the vibration and the pulverized active carbon would be drawn by suction into the carburetor. This would cause the carburetor to malfunction.
Various problems arise in the case of the arrangement of (2) in which particulate active carbon is packed between the folds of the folded air cleaner filter material layer of a filter element. These problems would include complication of the process for securing the particles of active carbon in place, the need to perform a time-consuming operation of packing the particulate active carbon in the folds of the filter material layer, and obturation of the filter material layer of the air cleaner element by the pulverized active carbon as the result of the wear caused by the vibration of the engine on the active carbon.